1. Field of the Invention
The present invention relates to a scanning probe microscope and a scanning method capable of providing a distribution of information of a shape or a physical property of a surface of a sample by scanning the surface of the sample by vibrating a stylus above the surface of the sample.
2. Description of the Related Art
In a related art, there is known a scanning probe microscope including a scanning tunnel microscope or an atomic force microscope with an object of observing a fine shape or a material physical property of a sample for providing information thereof by scanning a surface of a sample by a stylus.
Taking an example, there is known an ultra low force atomic force microscope for observing a shape or the like of a surface of the sample by scanning the surface by vibrating a stylus in a vertical direction relative to the surface of the sample while maintaining an average distance to the surface of the sample constant (refer to, for example, Japanese Patent Specification No. 2732771).
In the ultra low force atomic force microscope, that the stylus is vibrated in the vertical direction achieves an effect of weakening of an influence of a friction force operated between the stylus and the surface of the sample, or a surface tension by a surface adhering water layer constituting an adverse influence in scanning the stylus in parallel with the surface of the sample.
In recent years, small-sized formation and high degree formation of a working dimension is promoted in a technology of working a semiconductor or the like, and a necessity of measuring a fine shape of a structure having a high aspect ratio, or a steep inclined face constituting the structure have been increased.
According to a scanning probe microscope of a related art, observation data are acquired at constant sampling intervals. Therefore, when a high aspect shape mixed with a region having a steep inclination and a flat region is measured, in order to measure the steep inclination by a necessary shape resolution, it is necessary to take the sampling interval more densely than that of the flat region, and when the sampling interval is constant, a number of unnecessary sampling points is increased in the flat region.
In order to avoid the problem, a number of proposals have been made as methods of variably setting a sampling interval while measuring a shape data (for example, JP-A-2002-014025).
On the other hand, when a high aspect ratio shape is measured, other problem is also present. That is, in comparison with an amplitude of vibrating a stylus in a vertical direction in a normal ultra low force atomic force microscope, a variation in height direction is excessively large, and therefore, there is also a case in which it is difficult to accurately follow a shape in scanning. In recent years, as one of methods of avoiding the difficulty, there is proposed a scanning method of repeating an operation in which a stylus is moved down in a vertical (Z) direction at the sampling point to be proximate to a surface to thereby catch a shape and successively moved up to be remote therefrom and moved to a next sampling point, a so-to-speak SIS mode (refer to JP-A-2005-069851).
In the SIS mode, there are needed time periods of making the stylus proximate to and remote from the sample in distances therebetween for respective sampling points, and a time period required for a total of scanning is prolonged along with a number of sampling points. Therefore, an unnecessarily large number of the sampling points signifies a problem of an unnecessarily long measuring time period.
With regard to the problem, a method of variable sampling proposed in a scanning probe microscope of a background art is not applicable to the scanning probe microscope of the scanning method of JP-A-2005-069851 mentioned above. For example, the scanning probe microscope of JP-A-2002-014025 is applicable only to a scanning method in which a stylus always traces a surface, and is not applicable to the scanning probe microscope of JP-A-2005-069851 mentioned above.